The Water Hammer (whtd) interface (), found under the Fluid Flow > Single-Phase Flow branch () when adding a physics interface, is used to compute the velocity and pressure fields for propagation of a hydraulic transient, also known as a water hammer, in elastic pipe systems. For example, the propagation of a water hammer in a piping system of an oil refining plant.

When this physics interface is added, these default nodes are also added to the Model Builder — Fluid Properties, Pipe Properties, Closed, and Initial Values. Then, from the Physics toolbar, add other nodes that implement, for example, boundary conditions. You can also right-click Water Hammer to select physics features from the context menu.

The Label is the default physics interface name.

The Name is used primarily as a scope prefix for variables defined by the physics interface. Refer to such physics interface variables in expressions using the pattern <name>.<variable_name>. In order to distinguish between variables belonging to different physics interfaces, the name string must be unique. Only letters, numbers, and underscores (_) are permitted in the Name field. The first character must be a letter.

The default Name (for the first physics interface in the model) is whtd.